In holography, some of the light scattered from an object or a set of objects falls on a recording medium. A second light beam, known as the reference beam, also illuminates the recording medium, so that interference occurs between the two beams. The resulting light field is an apparent fringe pattern of varying intensity which is the hologram. It can be shown that if the hologram is illuminated by the original reference beam, a light field is diffracted by the reference beam which is identical to the light field which was scattered by the object or objects. Thus, someone looking into the hologram “sees” the objects even though they are no longer present. There are a variety of recording materials which can be used, including photographic film. Holograms can also be computer generated.
In the past holograms have usually been binarized by thresholding, or injecting noise signals into the holograms using methods such as the random phase or the error diffusion (or similar) methods. These approaches either result in poor and/or noisy reconstructed images, or the structural content is degraded, sometimes to the degree that no discernable image can be reproduced.
It has previously been shown through computer generated holography (CGH) that a three-dimensional object scene can be recorded as, or represented by, a binary hologram instead of a gray-scale hologram, i.e. the pixels forming the hologram comprise binary values rather than eight or sixteen bit grey scale values, for example. Binary encapsulation of holograms therefore allows the holograms to be recorded with much smaller data sizes, and enables the swift production of printed holographic images on suitable mediums using commodity printers which are only capable of outputting black and white dots. For static object scenes, this means of production is substantially lower in cost than the conventional use of a spatial light modulator, and also enables printing or display of very large holograms on suitable media. When a binary hologram is displayed on an electronically accessed display device, such as a spatial light modulator, the reconstructed image of the object scene recorded by the hologram is not affected by the non-linear characteristics of the display device. In addition, with binary holograms, the storage capacity of the binary holograms is enhanced and this facilitates much more efficient transmission of holograms over transmission media.
Investigations have been conducted to understand the causes of and address the distortions caused by quantization or digitizing of grey-scale holograms, but little, if anything, appears to have been done to address problems encountered with binary computer generated holograms which have been found to produce severe distortion upon reconstruction. In particular, if the original object is complicated, there may be no discernable reconstruction of the recorded image possible or the hologram will not allow the original object scene to be reproduced for viewing.